Injecting power line carrier signals onto power lines for the purpose of communicating digital data from one location to another is used in the field of power distribution. Typically, a power line carrier signal is generated by supplying a sinusoidal signal at the input of an amplifier. The signal is amplified and then injected onto the power line by injecting it into the secondary winding of a power transformer that is connected to the power line or injecting it directly onto the power line through high voltage capacitors. In the case of the transformer type injection, the signal that is injected into the secondary winding of the transformer induces a signal on the primary winding of the transformer which is connected to the power line. Digital data is communicated by modulating the phase of the carrier signal that is induced onto the power line.
For conventional power line carrier infrastructure, large capacitors may be used to couple the carrier signal onto the distribution lines. These large capacitors can be a safety concern as they are at distribution line potential (7.5 to 25 kV) and can store an electrical charge for a long period of time.
Another disadvantage of conventional power line carrier injecting systems is the complexity of the circuitry in such systems. The complexity of the circuitry can lead to higher manufacturing and maintenance costs.
Accordingly, a need exists within the art for a power line carrier injection device that can reduce or eliminate the use of large coupling capacitors and/or complex circuitry, that can increase the safety of the device, and/or that can allow for the device to be installed in a smaller enclosure.